Summary: Evidence for Pacific-modulated precipitation variability during the late
Holocene from the southwestern USA
Jessica B. T. Rasmussen,1
Victor J. Polyak,1
and Yemane Asmerom1
Received 12 January 2006; revised 2 March 2006; accepted 9 March 2006; published 18 April 2006.
[1] The mechanisms driving late Holocene drought cycles
in the western United States are not well known due to the
general scarcity of long-term, high-resolution, absolutely
dateable proxies for precipitation in continental interiors.
Here we show that late Holocene precipitation variability in
the southwestern United States has been caused by changes
in the Pacific Ocean. We present a stalagmite-based,
annually resolved moisture record that indicates large
shifts from pluvial to drought conditions alternating with
periods of dampened, near-average precipitation over the
last 3000 years. Significant spectral peaks at decadal-scale
($20­50, 70­80 year) frequencies likely correspond to
modern frequencies of the Pacific Decadal Oscillation or a
low-frequency component of the El Nin~o-Southern